1. Field of the Invention
The present invention relates to a manufacturing method for an optical waveguide which is widely used in optical communication, optical information processing, position sensors, and other fields of general optics, and an optical waveguide body used therefor.
2. Description of the Related Art
In general, in signal transmission using optical wiring, an optical connector is used to couple optical fibers and/or optical waveguides. The optical connector includes a band-like optical waveguide, and a connection terminal having a predetermined shape called “ferrule”, which is mounted to a longitudinal end portion of the optical waveguide and has guide holes into which guide pins for alignment may be inserted. As such a ferrule, in general, a PMT ferrule described in JPCA Standards “Detail Specification for PMT Connector” (JPCA-PE03-01-07-(2006)) is often used. In an optical connector using such an optical waveguide, the optical connector is inserted from one insertion opening of an optical waveguide fixing through hole of the PMT ferrule described the JPCA Standards “Detail Specification for PMT Connector” (JPCA-PE03-01-07-(2006)), and is fixed with one longitudinal end surface of the optical waveguide being exposed at the other opening of the through hole provided at a connection end surface of the ferrule having guide holes. The optical connector manufactured in this way is aligned and coupled by the above-mentioned guide pins and guide holes. Here, if the contour of the optical waveguide and a core in the optical waveguide are misaligned, efficient optical connection cannot be achieved at the coupled portion. That is, in order to achieve efficient optical connection, it is necessary to secure the positional accuracy between the contour of the optical waveguide and the core.
By the way, the optical waveguide used in the above-mentioned optical connector is ordinarily constructed by forming the core as an optical path in a predetermined pattern on a front surface of an undercladding layer and forming an overcladding layer so as to cover the core. In such an optical waveguide, all of the undercladding layer, the core, and the overcladding layer are formed using a polymer material. Such an optical waveguide formed of a polymer material is generally manufactured through patterning of the core by photolithography, a stamper, and photobleaching. When the patterning is carried out, a mark as a positional reference is sometimes formed together with the pattern of the core.
The optical waveguide manufactured in this way is, for example, formed into a film shape, and, after the above-mentioned overcladding layer is manufactured, appropriately cut into a contour having a predetermined size and a predetermined shape by dicing, a laser, or the like. Here, the cut position is determined with reference to the above-mentioned core or mark provided as a positional reference, and the cutting is carried out with reference thereto.
On the other hand, the mark as the reference of the cut position of the optical waveguide manufactured by the above-mentioned method is, together with the core, covered with the overcladding layer. The difference in refractive index between the mark and the overcladding layer is small, and thus, there is a problem that the mark has poor visibility. Further, an upper portion of the patterned mark is often rounded, and thus, a border between the mark and another portion may be indistinct. In particular, when the above-mentioned mark which is formed together with the core is visually recognized using an image analyzer or the like, the recognition is very difficult. Even if the recognition is possible, it is difficult to secure sufficient accuracy.
In order to secure visibility of the above-mentioned mark, for example, there is proposed a method in which a mark for setting a position as a reference of the cutting is formed and fixed so as to protrude on a cladding layer, that is, on a surface of a film-like optical waveguide main body, and the cut position is determined and the cutting is carried out with the mark for setting the position being the reference (see Japanese Patent Application Laid-open No. 2010-72435).
However, in the method described in Japanese Patent Application Laid-open No. 2010-72435, the mark for setting the position is formed and fixed on the surface of the optical waveguide main body, and thus, there is a problem that misalignment occurs when the mark is fixed. The misalignment accumulates as an error when the cutting is carried out, and thus, even if the visibility of the mark is improved, it is difficult to, as a result, secure positional accuracy for the cutting which is sufficiently satisfactory.